Conventional methods and devices of the type described are based a following principle. When a constant voltage is supplied between two ones of terminals of a semiconductor integrated circuit, and when a beam such as a laser beam, electron beam, or a ion beam is projected to the semiconductor integrated circuit chip, a change of a current in the semiconductor integrated circuit is caused by a change of a temperature caused by beam irradiation and heating of the semiconductor integrated circuit. The change of the current (.DELTA.I) is defined by an equation (1). EQU .DELTA.I=(.DELTA.R/R)I (1)
In the equation (1), R represents a resistance of the circuit when the chip is not supplied with the beam, .DELTA.R represents a change of the resistance of the circuit when the chip is supplied with the beam and heated, I represents a current of the circuit when the chip is not supplied with the beam.
In this event, R is constant. Therefore, it is possible to detect a product of .DELTA.R and I by detecting .DELTA.I. In addition, it is possible to detect .DELTA.R when I is constant. Also, it is possible to detect I when .DELTA.R is constant.
A first conventional method or device is disclosed in Japanese Unexamined Patent Prepublication (Kokai) No. 300824/1994. This first conventional method comprises a fist step of projecting the beam on the chip during scanning the beam while a constant voltage is supplied to the circuit, and a simultaneous second step of detecting a change of a current in the circuit.
When conditions of the beams are same and when qualities of the material portions (if the chip supplied with the beam are same, differences of .DELTA.R in the portions of the chip are caused by differences of heat conduction in the portions of the chip. If there is a fault that the chip has voids and Si nodules, heat conduction in the portions of the chip, e.g., in Al interconnects that has voids and Si nodules are different. Therefore, this conventional method detects a change of a current in the circuit to detect voids and Si nodules in the portions of the chip, e.g., in Al interconnects
A second conventional method is disclosed in Japanese Patent Application No. 230672/1994. This second conventional method detects I when .DELTA.R is constant. A signal detected by the first and second conventional methods is hereinafter called BIRCH signal.
A third conventional method is disclosed in Publication of Extended Abstracts (The 55th Autumn Meeting, 1994): The Japan Society of Applied Physics; 22a-ZP 10, p. 586 of Koyama et al. This third conventional method is called an NBOBIC method. This third conventional method comprises a step of projecting a laser beam on the chip; and a simultaneous step of detecting a current of the chip while the chip is supplied with the laser beam. If there is a fault that the chip has voids, thermoelectric powers in the portions of the chip, e.g., in Al interconnects that has voids are different. As a result, thermoelectricmotives causes by differences of thermoelectric powers. Therefore, this conventional method detects changes of currents in the circuit that are caused by the thermoelectricmotives. A signal detected by the third conventional method is hereinafter called NBOBIC signal.
However, the conventional methods for using the laser beam or the electron beam have a disadvantage in that currents are generated in the chip because electron-hole pairs are generated in a semiconductor in a substrate of the chip.
A signal of the current generated by the electron-hole pair is hereinafter called OBIC signal. The OBIC signal is overlapped to the BIRCH signal. In addition, the OBIC signal is stronger than the BIRCH signal. Also, the conventional methods have a dynamic range which has not a width that is capable of amplifying both the OBIC signal and the BIRCH signal. Therefore, inasmuch as the conventional methods are incapable of distinguishing between the OBIC signal and the BIRCH signal, the conventional methods are incapable of detecting the BIRCH signal. Similarly, the conventional methods are incapable of detecting the NBOBIC signal. In addition, inasmuch as the conventional methods are incapable of distinguishing between a EBIC(Electron Beam Induced Current) signal and the BIRCH(and NBEBIC) signal, the conventional methods are incapable of detecting the BIRCH(and NBEBIC) signal.
Also, the conventional methods for using the ion beam have a disadvantage in that the ion beam sputters the chip to destroy the chip.